26: Obstructive Uropathy Flashcards
1
Q
Obstructive uropathy prevalence
A
- Hydronephrosis in 3.1%; ~2% kids
- M=F until 20yo, then F>M (pregnancy) until 60 (prostatic hyperplasia)
- M>F congenital/pediatric obstruction
2
Q
Unilateral obstruction
A
- 3 phases of RBF changes:
- First hour: ↑RBF + ↑tubule pressure 2/2 afferent arteriolar vasodilation (prostaglandins, NO)
- 3-4 hours: ↓RBF + ↑tubule pressure 2/2 afferent arteriolar vasoconstriction (RAS); tx w/ ACEi
- 5 hours: ↓RBF, ↓ tubule pressure 2/2 ↓GFR
3
Q
Bilateral obstruction
A
- 2 phases of RBF changes
- First 90 min: modest ↑RBF + ↑tubule pressure 2/2 prostaglandins, NO
- >90 min: ↓RBF
- Different from unilateral due to accumulation of vasoactive substances (ANP) in urine
4
Q
Partial obstruction
A
- In prenatal, may affect glomerular development permanently
- Likely 2/2 microvascular damage in glomeruli
- If <2wks, GFR returns to normal
- 1 mo, recover 30% GFR function
- >2 mos, recover 8% GFR function
5
Q
Pathophysiology of obstruction
A
- Obstruction disrupts mechanisms allowing for renal concentration of urine:
- Na+ reabsorption from TALH
- Flow of urea from inner medullary collecting duct
- Water permeability of collecting duct (aquaporins)
6
Q
Pathologic changes caused by obstruction
A
- Gross: 6wks: enlarged kidney + cystic dilation
- Micro:
- 7 days: dilated tubules, interstitial edema, dilation of Bowman’s space
- 12 days: papillary tip necrosis
- 16 days: thickened BM
- 5-6wks: glomerular collapse, interstital fibrosis, proliferation of connective tissue
7
Q
Causes of renal obstruction
A
- Congenital: cystic, UPJ obstruction
- Neoplastic: RCC, Wilms, urothelial, multiple myeloma
- Infx/Inflam: ecchinoccocus, TB, abscess, stricture, retroperitoneal fibrosis
- Metabolic: nephrolithiasis
- Other: trauma, renal artery aneurysm
8
Q
Causes of ureteral obstruction
A
- Congenital: ureterocele, megaureter, retrocaval ureter
- Neoplastic: cancers
- Infx/inflam: RPF, AAA, TB, stricture
- Metabolic: amyloidosis, stones
- Other: trauma, endometriosis, pregnancy
9
Q
Causes of bladder/urethral obstruction
A
- Congenital: posterior urethral valves
- Neoplastic: bladder, urethral, prostatic
- Infx/inflam: prostatitis, urethral stricture, phimosis
- Metabolic: amyloidosis, stones
- Other: BPH, neurogenic bladder
10
Q
Most common causes of upper UTO
A
- Nephrolithiasis
- Extrinsic (e.g., lymphadenopathy)
- Ureteropelvic junction obstruction
- Blood clot
11
Q
Most common causes of lower UTO
A
- Adult men:
- Benign prostatic hyperplasia
- Urethral stricture
- Adult women:
- Cervical cancer
- Uterine prolapse
- Pregnancy
12
Q
Ultrasonography
A
- No radiation or IV dyes (safe for peds, preg, renal insuff/failure)
- Differentiate btw. upper/lower UTO (dilated kidney calyx vs. bladder)
13
Q
Retrograde pyelography
A
- Invasive (cytoscopy + ureteral cath)
- Sensitive for localizing obstruction
- No IV dye (safe in renal insuf/failure)
- Potentially therapeutic (stent bypasses and clears obstruction)
14
Q
CT & MRI Scanning
A
- Sensitive + elucidate etiology
- IV dyes toxic (iodine in CT, gadolinium in MRI)
- High radiation dose in CT
- Pre-contrast, early/arterial phase, delayed phase (CT)
15
Q
Nuclear renography
A
- Evaluates functional obstruction
- T1/2 time used as estimation of obstructin
- 20 min = obstruction
- Estimates renal split function
